Brown recluse spider

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{{Taxobox | color = pink | name = Brown recluse spider | image = Brown recluse spider, Loxosceles_reclusa.jpg | image_width = 200px | regnum = Animalia | phylum = Arthropoda | classis = Arachnida | ordo = Araneae | familia = Sicariidae | genus = Loxosceles | species = L. reclusa | binomial = Loxosceles reclusa | binomial_authority = Gertsch & Mulaik, 1940 }}

The brown recluse spider is a venomous spider, Loxosceles reclusa, of the family Sicariidae (formerly of the family Loxoscelidae). It is usually between 1/4 and 3/4 inch (6.4-19.1mm) but may grow larger. It is brown and usually has markings on the dorsal side of its thorax, with a black line coming from it that looks like a violin with the neck of the violin pointing to the rear of the spider resulting in the nickname "fiddleback spider" or "violin spider". Coloring varies from light tan to brown and the violin marking may not be visible.

The brown recluse spider is native to the United States from the southern Midwest south to the Gulf of Mexico ([1]). The native range lies roughly south of a line from southeastern Nebraska through southern Iowa, Illinois, and Indiana to southwestern Ohio. In the southern states, it is native from central Texas to western Georgia.

Recluse spiders, which also include Mediterranean recluse spider (Loxosceles rufescens), build irregular webs that frequently include a shelter consisting of disorderly threads. Unlike most web weavers, they leave these webs at night to hunt. People get bitten when they unintentionally squeeze them in clothing and bedding.

These spiders frequently build their webs in woodpiles and sheds, closets, garages, and other places that are dry and generally undisturbed.

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A venomous bite

Image:Brown recluse.jpg As indicated by its name, this spider is not aggressive and usually bites only when disturbed. Actual brown recluse bites are rare and few brown recluse spiders are large enough to bite through skin. The initial bite frequently cannot be felt. Most bites are minor with no necrosis, but a small number produce severe dermonecrotic lesions or even systemic conditions (viscerocutaneous loxoscelism) with occasional fatalities. (For a comparison of the toxicity of several kinds of spider bites, see the list of spiders having medically significant venom.)

It is estimated that 80% of reported brown recluse bites may be misdiagnoses. The misdiagnosis of a wound as a brown recluse bite could delay proper treatment of serious diseases ([2]). There is now a test for brown recluse venom that can determine if a wound is a brown recluse bite.

The serious bites form a necrotising ulcer that destroys soft tissue and may take months to heal, leaving deep scars. The damaged tissue will become gangrenous and eventually slough away. Initially there may be no pain from a bite, but over time the wound may grow to as large as 10 inches (25 cm). Bites may take up to seven hours to cause visible damage; more serious systemic effects may occur before this time, as venom of any kind spreads throughout the body in minutes. Deaths (1.5% of all cases) have been reported for the related South American species L. laeta and L. intermedia.

First aid involves the application of an ice pack to control inflammation, and prompt medical care. If it can be easily captured, the spider should be brought with the patient in a clear, tightly closed container so it may be identified. However, by the time the bite is noticed any spider found nearby is not likely to be the culprit.

Reported cases of bites occur primarily in Texas, Kansas, Missouri, and Oklahoma. There have been many reports of brown recluse bites in California (and elsewhere outside the range of the brown recluse); however the brown recluse is not found in California ([3]) (though several related species may be found there). Many arachnologists believe that many bites attributed to the brown recluse in the West Coast are instead the bites of other spider species (such as the hobo spider, which produces similar symptoms, and is found in the northwestern United States), or else are not spider bites at all.

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Lookalikes

Sometimes, a spider of a different species may be mistaken for a brown recluse spider. These include the southern house spider. These species are generally harmless.

Male southern house spiders very closely resemble brown recluses, having similar coloration and body structure (though they have slender bodies and are uniformly brown, unlike the brown recluse). They mainly wander in search of females to mate with, having no particular territory. Females are more compact, dark brown or black, and rarely seen, building webs along crevices (for which reason they are also called crevice spiders); they seldom move except to capture prey caught in the web.

Southern house spiders may sometimes appear to be aggressive, but they do not bite unless trapped, and they are too small to easily penetrate human skin. They do, however, have an unnerving tendency to crawl across anything in their path regardless of whether it is alive. This is not aggression; these spiders are simply nearly blind and cannot see larger animals. Indeed, these spiders instinctively play dead if they feel threatened (a tactic which is effective against their common predators).

A spider playing dead will try to run if anything touches it, or bite if it cannot run.

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